Method of preparing cycloolefins



United States Patent O 3,243,468 METHOD OF PREPARING CYCLOOLEFINS Reginald F. Clark, Baton Rouge, La., and Charles D.

Storrs, Niagara Falls, N.Y., assignors, by mesne assignments, to Columbian Carbon Company, a corporation of Delaware No Drawing. Filed June 14, 1962, Ser. No. 202,383

22 Claims. (Cl. 260-666) This application is a continuation-in-part of application Serial No. 73,560 filed December 5, 1960.

This invention relates to catalytic reactions, particularly the formation of cyclic compounds having olefinic unsaturation in the ring from substituted and unsubstituted open chain conjugated diolefins. More specifically, the invention is in the catalysis of organic reactions by means coordination complexes of nickel in the zerovalent state, wherein four molecules of an organophosphorus, organoarsenic, and/ or organoantimony compound are coordinately bonded to the nickel.

The tetrakis complexes of groups VI and VIII metals of the periodic chart are fairly well known, but such complexes have been limited to the inorganic complexes. Such complexes as nickel tetrakistribromophosphine and nickel tetrakistrifluorophosphine are known (US. Patent No. 2,882,306). Such compounds are prepared by heating nickel tetracarbonyl with excess phosphorus trichloride in a steam bath, the carbonyl radicals being replaced by the phosphorus trichloride.

The tetra-substituted complexes of the prior art have been limited .to the inorganic complexes of nickel, and heretofore, the tetra-substituted organic complexes of nickel were unknown.

This invention provides a process of using such complexes, preferably, the tetrakis (triorganophosphorus) nickel complex catalysts, and still more preferably the tetrakis (triarylphosphite) nickel complex catalysts, which will give a high conversion and a good selectivity for catalyzing oragnic reactions.

Various advantages of the present invention will become apparent to those skilled in the art from the accompanying description and disclosure.

The tetra-substituted complexes of this invention may be represented by the following formula:

in which b, c, and d are the same or different and are cardinal numbers of zero or one. Alternatively these complexes may be represented by the following formula:

in which Z Z Z and Z are the same or dilferent compounds represented by the formula a a a in which M is phosphorus, arsenic, or antimony, although phosphorus is preferred; a is a cardinal number and is equal to one or zero; and R and R and R are the same or different organic radicals. These radicals may be substituted or unsubstituted hydrocrbons in which the substituents comprise hydrogen, carbon, oxygen and halogen. Examples of unsubstituted radicals which are suitable for use in this invention are alkyl radicals such as ice methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tertbutyl, amyl, isoamyl, hexyl, heptyl, octyl, isooctyl, dodecyl, and octadecyl; cycloalkyl radicals such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and cyclooctyl; aryl radicals such as phenyl, biphenyl, a-naphthyl, fi-naphthyl, a-anthryl, fl-anthryl, l-phenanthryl, Z-phenanthryl and 9-phenanthryl. Examples of substituted radicals which may be used are alkaryl such as tolyl, xylyl, Z-mesityl, duryl, cumenyl, aspseudocumyl, s-pseudocumyl, and v-pseudocumyl; cycloalkyl derivatives such as 3-methyl cyclopropyl, 3,4-dimethylcyclohexyl, 3-amylcyclohexyl and 3,5-dimethylcyclooctyl; aralkyl such as benzyl, phenet-hyl, m-tolylmethyl, l-mesityl, m-tolylethyl, 3-phenyl-l-propyl, and fi-naphthylmethyl; oxygen-containing radicals such as anisyl, salicyl, desyl, vanillyl, phenthyl, phenacyl, acetonyl, acetoxy, p-ethoxyphenyl, methoxymethyl, methoxyethyl, S-methoxycyclopentyl, and pacetophenyl; fluorine, chlorine, bromine and iodine-substituted radicals such as p-chlorophenyl, 2-chloroethyl, m-(t-rilluoromethyDphenyl, 3-bromocyclohexyl.

The bonding arrangement of these complexes, as shown by the dashed lines in the formula above, is believed to be a coordination bonding system completely lacking in ordinary valence bonds; thus the nickel atom of the complex is in the zero valence state.

It has been discovered that the nickel complexes of this invention may be prepared from nickel tetracarbonyl, monosubstituted nickel t-ricarbonyl, disubstituted nickel dicarbonyl, or trisubstituted nickel monocarbonyl, thus permitting the substituents to be the same or different.

The first of the starting materials used in the preparation of these complexes may be represneted by the following formula:

wherein b, c, and d are the same or difierent and are cardinal number-s of zero or one, and Z Z and Z have the foregoing significance. The carbon monoxide group or groups of the nickel-containing starting material are replaced by Z having the significance given above. The various nickel complexes containing carbonyl groups which are suitable starting materials for the complexes of this invention are known (US. patents numbered 2,686,208, 2,686,209, 2,839,510 and elsewhere).

The reactions which produce such nickel complexes may be presented in a general way by the following formulas:

It will be appartent to one skilled in the art that a wide variety of substitutions and mixtures of substitutions may be produced merely by varying the reagents added to the reaction at the various carbonyl subsitution stages. For example, if it were desired to produce tris(triphenylphosphite) mono(triphenylphosphine) nickel, such a product could be prepared by reacting one mole of mono (triphenylphosphine) nickel tricarbonyl with 3 moles of triphenylphosphite. Another method in which the same compound might be prepared would be to react one mole of tris(triphenylphosphite)nickel monocarbonyl with 1 mole of triphenylphosphine to produce the desired compounds.

Reactions 1, 2, and 3 listed above actually consist of a plurality of steps or stages which occur as the respective carbonyl groups are replaced. These steps or stages may be carried out in sequence or alternatively and preferably as a unitary reaction in which the reactants are added in the required amounts initially, and which requires only temperature and pressure control of the reaction vessel.

It has been found desirable to carry out the replacement reaction in the presence of stoichiometric excesses of the replacing compound; that is, more than 4 moles ing to Formula 2, the ratio of the complex to the substituting compound (Z should be from about 1:35 to about 1:7. When the tetra-substituted nickel complex is to be produced from the disubstituted nickel dicarbonyl according to Formula 3, the ratio of nickel complex to substituting compound (Z should be from about 122.5 to about 1:4. When the tetrasubstituted nickel complex is to be produced from the trisubstituted nickel monocarbonyl according to Formula 4, the molar ratio of the nickel complex to the substituting compound (Z is preferably from about 1:1.1 to about 1:2.

The molar ratios specified above are preferred ratios and reflect the use of quantities of phophorus-containing compounds which are from about to about 100% stoichiornetric excesses. The upper limitation, i.e., 100% is not critical. The use of 200% or even 300% excess may be desirable in some applications, since such excesses do not materially affect the reaction, but rather act as a diluent for the reaction mixture. Reacting the nickel complexes with less than 100% of the stoichio- .metric requirementsof phosphorus compound are useful under some conditions.

Since nickel tetracarbonyl is highly toxic and decomposes rather violently at temperatures above 60 C. at atmospheric pressure, it is preferable to initiate reaction represented by Formula 1 in a solvent and at temperatures below C., and complete the replacement of the first carbonyl group at this temperature. Temperatures up to about 40 C. may be used, but the 20 C. maximum is preferred. Completion of the first stage of the reaction is evidenced by a sharp decrease in the amount of carbon monoxide evolved. At'this point the danger of explosion is diminished since almost all of the nickel is in the form of a complex; thereafter other heating steps are commenced. The subsequent steps of Reaction 1, and Reactions 2, 3, and 4 are carried out by a rapid heating to above about 180 C., or by a gradual or stepwise heating in which the temperature is increased each time that carbon monoxide evolution substantially ceases.

When the stepwise method of heating is employed it has been found that the second and third carbonyl replacements take place at from about 120 C. to about 180 (3., depending upon the reactants used and to some extend upon the pressure in the reaction vessel. The final carbonyl replacement takes place at temperatures from about 140 C. to 270 C. or higher, but the preferred temperature for the final carbonyl replacement is from about 180 C. to about 230 C. At temperatures substantially above 230 C., i.e., 275 C., the reaction time is reduced, but the higher temperatures cause excessive product decomposition; therefore these temperatures are not preferred, but are useful for some applications. At temperatures much below 180 C., i.e., 135 C., the reaction time is greatly increased; therefore the lower ranges are not preferred. The time required for the reaction varies from about 1 hour to about 50 hours depending upon the temperature, pressure, starting material, and substitution compound employed. I

The reactions are carried out either with or without a solvent, with theexception mentioned above for the phere.

first stage of Reaction 1. Any solvent, such as a higher paraffin, which is inert with respect to the reactants and products and is liquid at the reaction temperatures and pressures, is suitable for use in this aspect of the invention. It is preferably, however, to carry out the subsequent substitutions without solvent, since the reactants, for the most part, are liquid at the reaction temperatures.

It is desirable to provide a means for removing the eflluent carbon monoxide from thereaction site. This is normally accomplished by venting the reaction chamber to atmospheric pressure through a gas trap means, but other means are useful.

It has also been found desirable to blanket the reactor with an inert gas such as nitrogen, argon or other rare gases, since the presence of more than minute quantities of oxygen tends to accelerate the decomposition of the complex product. In this connection it has been found that applying vacuum to the reaction chamber during the reaction may be useful under certain conditions.

As mentioned above, the concept of the present invention includes the utilization of similar nickel complexes in which arsenic or .antimony appears in the place of phosphorus.

The following examples will serve to illustrate the preparation of several organo-phosphorus nickel complexes, but it is understood that these examples are set forth merely for illustrative purposes and many other tetrasubstituted nickel complexes are within the scope of the present invention.

Example I A mixture of 3 moles of triphenylphosphite and 1 mole of bis (triphenylphosphite)nickel dicarbonyl was heated to a temeprature of 200 C. for about 18 hours under an argon atmosphere. The mixture was then cooled and dissolved in chloroform. This was followed by filtering the mixture and removing the chloroform by vacuum distillation. The remaining solid was washed with methanol and dried. Repeated extractions with acetone'removed all of the starting materials and any by-products such as the tris(triphenylphosphite)nickel carbonyl which were formed during the reaction. The insoluble white crystals (93 grams) were tetrakis(triphenylphospihte) nickel with a melting point of 147148 C. and a decomposition temperature of 168-l70 C. The tetrakis(triphenylphosphite) nickel is a white solid, insoluble in water, methanol and acetone but soluble in benzene, p-dioxane and tetrahydrofuran. It is stable in water and alkaline solutions, but slowly decomposes in the presence of acids or solutions having a pH below 7. The infrared spectrum of this compound is essentially identical to bis(triphenylphosphite)nickel dicarbonyl and tris(triphenylphospihte) nickel carbonyl with the exception of the carbonyl adsorption bands which are absent.

Analysis-Calculated for C H O P Ni: C, 66.53.; H, 4.65; Ni, 4.52. Found: C, 66.48; H, 4.82; Ni, 4.58.

Example II A mixture of 50 grams (0.068 mole) of bis(triphenyl phosphite)nickel dicarbonyl and grams (0.484 mole) of triphenylphosphite. was heated in a stirred flask at to 200 C. for about 8 hours under an argon atmos- Upon cooling to room temperature the mixture solidified. The solid was dissolved in benzene, filtered, .and treated with charcoal. Evaporation of the benzene left a white solid which was washed with methanol. The crystals remaining were filtered and extracted with two 30 ml. portions of cold acetone. The white crystals remaining (11.6 grams) were found to be tetrakis(tri'- phenylphospihte) nickel, while the acetone wash was phite)nickel monocarbonyl.

Example III One mole of tris(triphenylphosphite)nickel monocarbonyl was heated to 250 C. for 8 hours with 1.5 moles of triphenylphospihte under an atmosphere of argon. After cooling and dissolvin the mixture in benzene, the solution was filtered, treated with charcoal, and the benzene removed under vacuum. The resulting mixture was poured into methyl alcohol and a precipitate was formed. Following acetone extractions of the unreacted and undesired products, tetrakis(triphenylphospihte) nickel (102 grams) with a melting point of 146 to 148 C. was recovered.

Example IV A mixture of 100 grams (0.136 mole) of tris(triphenylphospihte)nickel monocarbonyl and 17 grams (0.065 mole) triphenylphosphine Was heated to 170 C. for 4 hours at a reduced pressure of 2 mm. Hg. After cooling, the mixture was slurried with methyl alcohol and filtered. The crystals obtained were dissolved in benzene, treated with charcoal and precipitated with methyl alcohol. There were obtained grams of a white solid, tris(tripl1enylphospihte)triphenylphosphine nickel, M.P. 124-126 C.

The nickel complexes listed in Table I have been prepared and the physical data for these complexes are presented therein.

' Although most of the tetra-substituted complexes are insoluble in many solvents, such as water and methanol, the purification step may be advantageously carried out by washing the tetrasubstituted nickel complexes in ketones such as acetone. It has been found that most of the tetrasubstituted complexes are acetone insoluble, while the remaining materials including the mono-, di-, and tri-substituted nickel carbonyls are acetone soluble.

The nickel complexes of this invention are useful for catalyzing many organic reactions, especially additiontype polymerization reactions. These complexes have been found to be extremely effective for producing cyclic polymers of substituted and unsubstituted conjugated acyclic diolefins in which the polymer molecule contains 2, 3, 4 or more monomer groups. The complexes of this invention are especially useful for the catalyst polymerization of 1,3-butadiene and other 1,3-diolefins to form polymeric cyclic compounds which contain four carbon atoms within the ring structure per monomer group and one carbon to carbon double bond per monomer group. Extensive experimentation has shown that these nickel complexes, when used as catalysts for the dimerization of butadiene, will give heretofore unknown and unexpectedly high selectivities in producing cycloocta-1,5-diene and at the same time will maintain the same high conversion percentages which are achieved through the use of some of the known nickel complexes containing carbonyl groups.

It has also been found that by varying the operating conditions, high yields of trimers and other higher molectotal weight of product Weight of feed Weight of single product total Weight of product Weight of single product W Conversion Selectivity Yield= X 100 Yield equals the selectivity multiplied by the conversion and divided by 100.

The following examples serve to illustrate the use of the nickel complexes of this invention as catalysts for the dimerization of butadiene. Although the dimerization reaction is the sole illustration, other organic reactions may be catalyzed within the scope of this invention.

The following procedure was observed in the examples set forth below. The reactions using the nickel complexes as catalysts were carried out in a 500 ml. Magne Dash autoclave. The autoclave was thoroughly cleaned and the catalyst was added to the autoclave. The head ofthe autoclave was then put intoplace and tightened. The autoclave was then evacuated using a vacuum pump and the butadiene was added from a bomb.

The diolefins useful according to the invention are those produced by conventional processes. For instance, the butadiene used in the following examples was prepared in a commercial plant by the dehydrogenation of butene, followed by purification with cuprous ammonium acetate. A crystalline complex of the' cuprous ammonium acetate with butadiene is formed, and the butadiene is released from. the complex by the application of heat. As has been known .since 1950 and earlier, from commercial butadient plant operation in this country, this process gives butadiene of about to 99% purity with little variation for a given set of conditions.

The butadiene used in the following examples was ordinary plant butadiene not subjected to any particular purification procedures, except in most cases the material was passed through a column of silica gel to remove excessive amounts of.water and apparently a substantial proportion of the polymerization inhibitors such as paratertia-ry butylcatechol. The butadiene was obtained from the plant of Petroleum Chemicals Incorporated, Lake Charles, Louisiana. Analyses of butadiene, typical of the butadiene which was used in these examples are as follows Proportion Component: by weight, percent Butadiene-1,3 98.36 Isobutane 0.00

n-Butane 0.00 Isobutylene 0.025 Trans-butene-Z 0.065 Cis-butene-2 0.065 Propylene 0.58 Propadiene 0.075 Butadiene-1,'2 0.10 Acetylenes (including methylacetylene,

ethylacetylene,

vinylacetylene, and Y dimethylacetylene) 0.06 Carbonyl 0.002 Water 0.02

Isobutane and n-butane are commonly present in small amounts. The total acetylenes commonly range from about 0.05% to 0.09% by weight in butadiene of about 98.5% purity. The acetylenic constituents of a similar .clave.

butadiene' sample were analyzed by gas chromatography, and the following compounds and amounts were found:

Component: Mole, percent Methylacetylene 0.02 Ethylacetylene 0.04 Dimethylacetylene 0.01

'Vinylacetylene 0.002

As can be seen, the diolefin as used in the examples contained other unsaturated hydrocarbons having 3-4 carbon atoms.

' Example I 102 grams of butadiene were charged with 1.8 grams of tetrakis(triphenylphosphite) nickel into the autoclave. The autoclave was heated to 160 C. for about 30 minutes. After cooling and venting the unreacted butadiene, 74.5 grams of material were removed from the auto- Analysis of this material gave 74.1% of cycloocta-1,5-diene, 14.3% of vinylcyclohexene and 11.6% of material with a boiling point above cycloocta-1,5-diene. The conversion (percentage of butadiene reacted) was 71.2%.

' Example 11 102 grams of butadiene were charged, with 1.5 grams of tetrakis(triphenylphosphite) nickel, into the autoclave. The autoclave was heated to 148 C. for about 45 mirrutes. After cooling and venting the unreacted butadiene, 89 grams of material (conversion of 86%) were removed from the autoclave.- Analysis of this material showed 71.8% cycloocta-1,5-diene, 13.9% vinylcyclohexene, and 14.3% high boiling material.

Example III 101 grams of butadiene were charged with 1.5 grams of bis(triphenylphosphite)bis(triethylphosphite) nickel into the autoclave. The autoclave was heated to 148 C. .for about 323 minutes.

, After cooling and venting the unreacted'butadiene, 77 grams of material (conversion 76%) were removed from the autoclave. Analysis of this .material showed 40.2% cycloocta-1,5-diene, 37.1% vinylcyclohexene, and 22.7% high boiling material.

The, results of several more butadiene d-imerization runs -using tetrakis(triphenylphosphite) nickel are presented below in Table II.

-. a TABLE II Catalyst Coneen- Infrared Analysis tration based on Time, C. Converweight of feed Min. Temp. sion COD VCH HEM COD=cyc1oocta 1',5 diene; VCH=vinyleyclohexene; HBM=n1aterial which has a boiling point above that of COD.

Example IV invention are useful for continuous reactions as well as liquid at dimerigation temperature, the complexes ofv this invention may be used alone or, with other compatible catalysts in fluid bed reactors or like equipment. Variations in the method of employment will be obvious to one skilled in the art.

The reaction temperatures and pressures employed with the catalyst of this invention are determined by the product which is to be produced. Temperatures of from about 90 C. to about 160 C. have been found to yield the highest conversions of butadiene using tetrakis(triphenylphosphite) nickel, but ranges of from about C. to about 200 C. are operable. Optimum temperatures for other nickel complexes fall generally within the 70 C. to 200 C. range. When other monomers are used and/or other products than cycloocta-1,5-diene are to be produced, the temperatures employed may vary somewhat beyond the ranges specified herein.

Although the pressures used in the reaction vessel are not critical, pressures from about 15.75 to about 29.75 kilograms per square centimetre gauge are preferred. Pressures substantially less than 15.75 kilograms per square centimetre gauge are operable but the reaction time is increased to an undesirable extent. The specified higher pressures are limited to some extent by the equipment in which the reaction is conducted. Pressures exceeding 29.75 and up to 70 kilograms per square centimetre gauge or higher are useful for producing cycloocta- 1,5-diene, but such pressures are more applicable for producing trimers or other higher polymers.

Catalyst concentrations of about 0.5% to about 1.5% based on the weight of the monomer feed are preferred, but concentrations of from about 0.1 to about 10% on the same basis are useful for producing cycloocta-1,5- diene. Wider ranges of catalyst concentration, suchas 0.001 to 10%, are useful in this and other applications. Conversions of from to with 83% or higher cycloocta-l,5-diene selectivities in butadiene dimerizations with the nickel complexes of this invention have been obtained by using the preferred temperatures, pressures, and catalyst concentrations.

The scope of this invent-ion is not to be limited to the use of butadiene. Generally, unsaturated hydrocarbons can be polymerized with the catalysts of this invention. Monomers containing conjugated unsaturation such as isoprene, chloroprene, and the like are useful for dimerization, trimerization and like polymerization processes and are preferred. Other suitable conjugated open-chain diolefins, particularly 1,3-diolefins include 1.3-.pentadiene (piperylene); phenyldiolefins; 2,3-dichloro-l,3-butadiene; and 2,3-dimethyl-l,3-butadiene. The halogen-substituted conjugated open-chain diolefins preferably have no more than two halogen atoms substituted for hydrogen in each diolefin molecule. Mixed halogen derivatives :also may be used.

Auxiliary materials such as dehydrating agents, polymerization inhibitors, and catalyst activators may be used with the catalysts of this invention. 'The forms of the invention herein shown and described are to be considered only as illustrative.

We claim:

1. A method of catalyzing an organic reaction which comprises subjecting said reactant to the influence of a nickel complex represented by the formula Z4 Z -,I IlZ l.

in which Z Z Z and Z are of the formula M .R .Ro o.Ro

in which M is selected from the group consisting of phosphorous, arsenic, and antimon a is a cardinal uumberof from zero to one; and R R and R are organic radicals and are selected from hydrocarbon radicals and substituted hydrocarbon radicals in which the substitlleuts 6 m- 9 prise at least one of the elements carbon, hydrogen, oxygen and halogen.

2. A method of catalyzing an organic resaction which comprises subjecting said reactant to the influence of a nickel complex represented by the formula Z4 Z I IiR in which Z Z Z and Z are of the formula a a a in which a is a cardinal number of from zero to one; and R R and R are organic radicals and are selected from hydrocarbon radicals and substituted hydrocarbon radicals in which the substituents comprise at least one of the elements carbon, hydrogen, oxygen and halogen.

3. A method of polymerizing unsaturated monomers which comprises subjecting said monomer to the influence of a nickel complex represented by the formula Z4 Z l IiZ in which Z Z Z and Z are of the formula a E a in which M is selected from the group consisting of phosphorous, arsenic, and antimony; a is a cardinal number of from zero to one; and R R and R are organic radicals and are selected from hydrocarbon radicals and substituted hydrocarbon radicals in which the substituents comprise at least one of the elements carbon, hydrogen, oxygen and halogen.

4. A method of polymerizing unsaturated monomers which comprises subjecting said monomer to the influence of a nickel complex represented by the formula Z4 z 1lnz it in which Z Z Z and Z are of the formula a a 'a in which a is a cardinal number of from zero to one; and R R and R are organic radicals and are selected from hydrocarbon radicals and substituted hydrocarbon radicals in which the substituents comprise at least one of the elements carbon, hydrogen, oxygen and halogen.

5. A method of polymerizing as described in claim 4, wherein said monomer comprises an acyclic conjugated diolefin.

6. A method of polymerizing substituted or unsubstituted acyclic conjugated diolefin monomers to produce cyclic hydrocarbons containing at least 8 carbon atoms in the ring and having at least two carbon to carbon double bonds within the ring, which comprises subjecting said monomers to the influence of a nickel complex of the formula:

in which Z Z Z and Z are of the formula in which a is a cardinal number of from zero to one; and R R and R are organic radicals and are selected from hydrocarbon radicals and substituted hydrocarbon radicals in which the substituents comprise at least one of the elements carbon, hydrogen, oxygen and halogen.

7. A method of polymerization as described in claim 6, in which the monomer is 1,3-butadiene.

8. A method of polymerization as described in claim 6,

in which the nickel complex is tetrakis(triphenylphosphite nickel.

9. A method of polymerization as described in claim 6 in which the nickel complex is tetrakis(tri-p-methoxyphenylphosphite) nickel.

10. A method of polymerization as described in claim 6 in which the nickel complex is tetrakis(tri-p-tolylphosphite) nickel.

11. A method of polymerization as described in claim 6 in which the nickel complex is tetrakis[tri(2-ethylhexyl)phosphite]nickel.

12. A method of polymerization as described in claim 6 in which the nickel complex is tris(triphenylphosphite) triphenylphosphine nickel.

13. A method of polymerization as described in claim 6 in which the nickel complex is bis(triphenylphosphite) bis(triethylphosphite)nickel.

14. The method of claim 6 in which a is one.

15. The method of claim 14 in which each of R R and R comprise aryl radicals.

16. A method of polymerizing substituted or unsubstituted acyclic conjugated diolefin monomers to produce cyclic hydrocarbons containing at least 8 carbon atoms in the ring and having at least two carbon to carbon double bonds within the ring, which comprises subjecting said monomers to the influence of a nickel complex of the formula:

in which Z Z Z and Z are of the formula in which M is selected from the group consisting of phosphorous, arsenic, and antimony; a is a cardinal number of from zero to one; and R R and R are organic radicals and are selected from hydrocarbon radicals and substituted hydrocarbon radicals in which the substituents comprise at least one of the elements carbon, hydrogen, oxygen and halogen.

17. The method of claim 16 in which said diolefin is 1,3-butadiene, M is phosphorous, a is one, and R R and R consist of aryl radicals.

18. A method of polymerizing as described in claim 16', in which the monomer is 1,3-butadiene.

19. A method of polymerizing as described in claim 18, in which the cyclic hydrocarbons comprise cyclooctadiene and cyclododecatriene.

20. The process of claim 16 which is conducted in the presence of an organic solvent.

21. The process of claim 16 in which said diolefin is impure 1,3-butadiene containing other unsaturated hydrocarbons.

22. The process of claim 21 in which said other unsaturated hydrocarbons comprise acetylenic compounds.

References Cited by the Examiner UNITED STATES PATENTS 2,212,112 8/1940 Clausen 260666 2,373,811 4/1945 Cook et al 260439 2,461,961 2/1949 Buckmann et al. 260439 2,686,208 8/1954 Reed 260666 2,686,209 8/1954 Reed 260666 2,943,117 6/ 1960 Gleason 260666 3,076,016 l/1963 Leto et al. 260666 DELBERT E. GANTZ, Primary Examiner.

TOBIAS E. LEVOW, ALPHONSO D. SULLIVAN, Examiners.

E. C. BARTLETT, C. E. SPRESSER,

Assistant Examiners. 

3. A METHOD OF POLYMERIZING UNSATURATED MONOMERS WHICH COMPRISES SUBJECTING SAID MONOMER TO THE INFLUENCE OF A NICKEL COMPLEX REPRESENTED BY THE FORMULA 